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- ItemChronology of Cauvery Delta Sediments from Shallow Subsurface Cores Using Elevated-Temperature Post-IR IRSL Dating of Feldspar(Warsaw : De Gruyter, 2010) Alappat, L.; Tsukamoto, S.; Singh, P.; Srikanth, D.; Ramesh, R.; Frechen, M.We present the results of luminescence dating of sediments from two cores from the Cauvery Delta in south-east India. Since all natural quartz OSL signals except one sample were in saturation, the elevated temperature post-IR IRSL protocol for K-feldspar was applied to establish a chronology. Internal dose rates of K-feldspar grains were calculated from the measured internal content of potassium, uranium, thorium and rubidium in the bulk of K-feldspar grains using solution ICP-OES and ICP-MS analysis. A substantial scatter in single-aliquot De values was observed which is most probably due to the effect of incomplete bleaching of fluvial sediments before burial. A minimum age model was applied to extract possible depositional ages. The study revealed that except an upper layer of Holocene sediments (< 5m), the majority of the upper ~50m of Cauvery delta sediments were deposited between marine isotope stage MIS-5 and MIS-10 or older. The feldspar luminescence ages also indicate the existence of a period of non deposition or erosion in the upper part of the cores. © 2010 GADAM Centre Institute of Physics, Silesian University of Technology. All rights reserved.
- ItemOn the applicability of post-IR IRSL dating to Japanese loess(Warsaw : De Gruyter, 2011) Thiel, Christine; Buylaert, Jan-Pieter; Murray, Andrew; Tsukamoto, SumikoRecent work on infrared stimulated luminescence (IRSL) dating has focussed on finding and testing signals which show less or negligible fading. IRSL signals measured at elevated temperature following IR stimulation at 50°C (post-IR IRSL) have been shown to be much more stable than the low temperature IRSL signal and seem to have considerable potential for dating. For Early Pleistocene samples of both European and Chinese loess natural post-IR IRSL signals lying in the saturation region of the laboratory dose response curve have been observed; this suggests that there is no significant fading in nature. As a contribution to the further testing of post-IR IRSL dating, we have used 18 samples from two Japanese loess profiles for which quartz OSL and tephra ages up to 600 ka provide age control. After a preheat of 320°C (60 s), the polymineral fine grains (4–11 μm) were bleached with IR at 50°C (200 s) and the IRSL was subsequently measured at 290°C for 200 s. In general, the fading uncorrected post-IR IRSL ages agree with both the quartz OSL and the tephra ages. We conclude that the post-IR IRSL signal from these samples does not fade significantly and allows precise and accurate age determinations on these sediments.
- ItemThe Characteristics of OSL Signal from Quartz Grains Extracted from Modern Sediments in Japan(Warsaw : De Gruyter, 2010) Tokuyasu, Kayoko; Tanaka, Kazuhiro; Tsukamoto, Sumiko; Murray, AndrewQuartz grains from sediments in Japan are derived from complex mixtures of sources, including volcanic, plutonic, metamorphic and sedimentary rocks. We have measured the OSL signal of quartz grains from modern coastal sediments derived from different source rocks and compared these characteristics with the likely source. Each sample shows a different combination of various OSL components. It is concluded that the source rock affects the characteristics of the OSL components from quartz grains in Japanese sediments. By comparing the LM-OSL signals from volcanic sources with those from various source rocks, it can be deduced that quartz which has a higher fast component ratio is more suitable for dating. We also conclude that volcanic source areas should be avoided. © 2010 GADAM Centre Institute of Physics, Silesian University of Technology. All rights reserved.
- ItemGeoarchaeological studies on Roman time harbour sediments in Cologne — comparison of different OSL dating techniques(Warsaw : De Gruyter, 2011) Lauer, Tobias; Bonn, Rainer; Frechen, Manfred; Fuchs, Magret; Trier, Marcus; Tsukamoto, SumikoDue to the construction of a new North-South subway in Cologne, Roman time harbour sediments were exposed and were sampled for luminescence dating. A very good independent age control was given by the precise knowledge of the chronology of Roman activity and by radiocarbon ages of charcoal samples. Hence, different methodological approaches within luminescence dating were applied for Holocene heterogeneously bleached fluvial samples and were compared to the known ages. For one sample, optically stimulated luminescence (OSL) dating was applied to coarse-grained quartz using a single aliquot regenerative-dose (SAR) protocol. After De-measurements, dif-ferent statistical approaches were tested (i.e. arithmetic mean, median, minimum age model, finite mixture model, leading edge method and the Fuchs and Lang approach). It is demonstrated that the Fuchs and Lang approach along with the leading edge method yielded the best matching OSL ages with respect to the known ages. For the other sample which showed feldspar contamination within the quartz signal, the post-IR blue stimulated luminescence (double SAR protocol) was measured in three different ways to calculate the De-value: with continuous wave (CW) stimulation with an IR-bleach at 50°C and at 225°C for 100 s prior to the OSL, and pulsed OSL (POSL). It was demonstrated that the IR-stimulation at 225°C has very good potential to remove the feldspar signal contribution as well as pulsed OSL, but the former might deplete parts of the quartz OSL signal. © 2011 Silesian University of Technology, Gliwice, Poland. All rights reserved.
- ItemIRSL and post-IR IRSL residual doses recorded in modern dust samples from the Chinese Loess Plateau(Warsaw : De Gruyter, 2011) Buylaert, Jan-Pieter; Thiel, Christine; Murray, Andrew; Vandenberghe, Dimitri; Yi, Shuangwen; Lu, HuayuUsing a set of modern/young (0 to about 200 years old) dust samples collected from the Chinese Loess Plateau the bleachability of IRSL measured at 50°C (IR50) and post-IR50 elevated tem-perature IRSL (measured at 225°C and at 290°C) is investigated by measuring the apparent (residual) doses recorded by these signals. Doses recorded by quartz OSL are used as a reference. Allowing for differences in dose rates it seems that both IRSL and post-IR IRSL signals yield residual doses that are significantly larger than the doses measured in quartz. These residual doses can be largely ex-plained by thermal transfer caused by preheating. Nevertheless, we advise against the use of a low temperature preheat (<200°C) with IR50 to date loess samples because, as has been reported before, the signal appears to be thermally unstable. In general, we conclude that it may not be advisable to apply post-IR IRSL dating to Chinese loess samples where residuals of up to ∼20 Gy are a significant fraction of the total dose. However, these residuals quickly become unimportant when dating older samples, and this is the age range in which post-IR IRSL dating is likely to be most useful. © 2011 Silesian University of Technology, Gliwice, Poland. All rights reserved.
- ItemInfrared radiofluorescence (IR-RF) dating of middle pleistocene fluvial archives of the Heidelberg Basin (Southwest Germany)(Warsaw : De Gruyter, 2011) Lauer, Tobias; Krbetschek, Matthias; Frechen, Manfred; Tsukamoto, Sumiko; Hoselmann, Christian; Weidenfeller, MichaelThe infrared radiofluorescence (IR-RF) dating technique was applied to eight fluvial samples that were collected from two sediment cores at the Heidelberg Basin located near Viernheim and Ludwigshafen in southwest Germany. Based on the IR-RF derived ages of the samples it was possible to establish a chronological framework for the Mid-Pleistocene fluvial deposits of the Heidelberg Basin. The results allow us to distinguish between four main periods of aggradation. The lowermost sample taken from 100 m core depth lead to an IR-RF age of 643 ± 28 ka pointing to a Cromerian period of aggradation (OIS 17-16). For the Elsterian it is now possible to distinguish between two aggradation periods, one occurring during the Lower Elsterian period (OIS 15) and a second during the Upper Elsterian period (OIS 12-11). For the so called Upper interlayer (or "Oberer Zwischenhorizont" - a layer of organic-rich and finer-grained deposits), the IR-RF results point to a deposition age of around 300 ka, with samples taken directly on top and out of this layer yielding IR-RF ages of 288 ± 19 ka and 302 ± 19 ka, respectively. Hence, the measured IR-RF ages clearly point to a deposition during the Lower Saalian period (OIS 9-8) whereas earlier studies assumed a Cromerian age for the sediments of the Upper Interlayer based on pollen records and also mollusc fauna. The new IR-RF dataset indicates that significant hiatuses are present within the fluvial sediment successions. In particular the Eemian and Upper Saalian deposits are missing in this part of the northern Upper Rhine Graben, as the 300 ka deposits are directly overlain by Weichselian fluvial sediments. It is obvious that time periods of increased fluvial aggradation were interrupted by time periods of almost no aggradation or erosion which should have been mainly triggered by phases of increased and decreased subsidence of the Heidelberg Basin. © 2011 Silesian University of Technology.
- ItemMethodological Aspects on Luminescence Dating of Fluvial Sands from the Moselle Basin, Luxembourg(Warsaw : De Gruyter, 2010) Cordier, S.; Frechen, M.; Tsukamoto, S.Optically stimulated luminescence (OSL) dating of quartz and infrared-stimulated luminescence (IRSL) dating of feldspar were applied to fluvial sands from the lower terrace (M1) of the Moselle valley in Luxembourg (western Europe). The dating results indicated that the aggradation period for the sediments from below the M1 alluvial terrace can be correlated to the Weichselian upper Pleniglacial (MIS 2), which is in good agreement with the general chronostratigraphy of the Moselle terrace staircase. The ages were obtained from small aliquots of quartz and feldspars, using the single aliquot regenerative (SAR) protocol. The equivalent dose determination included a series of tests and the selection of the Minimum Age Model as the most appropriate statistical model. This made it possible to provide a reliable methodological background for further luminescence dating of fluvial sediments from the Moselle basin.
- ItemOptical dating of alluvial deposits at the orogenic front of the andean precordillera (Mendoza, Argentina)(Warsaw : De Gruyter, 2012) Schmidt, Silke; Tsukamoto, Sumiko; Salomon, Eric; Frechen, Manfred; Hetzel, RalfWell constrained numerical ages of alluvial fan sediments are key to understanding the chronology of alluvial episodes and tectonic activity at the front of the Andean Precordillera. We test-ed the application of radiocarbon and optically stimulated luminescence (OSL) dating in the distal part of an alluvial fan five kilometers north of Mendoza. For OSL dating a large number of aliquots (n > 70)-each composed of ̃50 quartz grains-were measured in order to obtain reliable burial ages despite scattered dose distributions. Owing to a feldspar contamination in all samples, an infrared stimulation was inserted before each OSL measurement, which reduced the feldspar OSL signal suc-cessfully. By using the minimum age model we obtained stratigraphically consistent burial ages of al-luvial deposits in a depth profile. The uppermost ̃1 m of sediment is composed of debris flow depos-its buried 770±76 years ago. Three plant remnants used for radiocarbon dating from the same layer, however, yielded ages younger than 350 years, which are interpreted to underestimate the deposition-al age. Underneath the debris flow, a major unconformity cuts a series of distal alluvial fan sediments with interstratified floodplain deposits, which are composed of sandy and calcite-rich silt layers, re-spectively. Three samples from this unit which were distributed over one meter of sediment thickness yielded statistically concordant OSL ages of 12.3±1.2 ka, 12.3±1.2 ka, and 11.7±1.1 ka. The deposi-tion of these sediments during the latest Pleistocene coincides with a phase of cool and humid cli-mate, which occurred before the alluvial fan propagated farther into the foreland. The overlying de-bris flow sediments are associated with alluvial fan incision during the arid Late Holocene. © 2011 Silesian University of Technology.